FIG. 88 is a conceptual diagram showing the structure and operation of a conventional automatic disc-changing apparatus as disclosed, for example, in Japanese Patent Kokai Publication 36365/1984 (Showa 59-36365). The significance of the symbols used in FIG. 88 is as given in FIG. 98.
In FIG. 98, "fixed" refers to a state in which two members do not move with relation each other, "engaged" refers to a state in which two members are mounted with an interrelationship between them (the two members are not fixed), "immovable" refers to a state in which the member is fixed with respect to chassis; and "butt contact" refers to a state in which the end of one member is touching against another member.
As is shown in FIG. 88, a conventional automatic disc-changing apparatus has as its principle constituents a player 1 supported on a chassis 5; a magazine rack 3 that accommodates compact discs resting on support pans 28; an elevator 2 that is capable of vertical travel along guide rails 14a, 14b and 14c and accommodates the magazine rack 3; and a carrier 4 mounted at the rear place of the player 1 and the elevator 2 (the upper left-hand portion in FIG. 88) but in this figure shown in the upper portion and causing movement of the compact discs in the magazine rack 3, together with support pan 28.
The apparatus shown in FIG. 88 moves in the following manner. The user first places compact discs on a plurality of support pans 28 (of which only one is shown in the figure), inserts the support pans 28 into a shelf-like structure 27 in the magazine rack 3, and inserts the magazine rack 3 into the elevator 2.
Then, by causing a rotating shaft 57 of a motor 56 to rotate, rollers 54 and 55, over which a belt 58 has been passed, also rotate, thereby rotating screw rods 52 and 53 which are fixed to them, and raising an elevating frame 8 which has threaded holes 50 and 51, into which the rods 52 and 53 screw. At this time the upper edge 8a of the elevating frame 8 makes butt contact with an arm 9a supporting a pressure ring 9, causing the pressure ring 9 to move upward. Simultaneously with this action, the elevator 2 is caused to ascend or descend by a winder 15, which is driven by the rotation of a motor 15a, by means of which a suspension cord 18, from which the elevator 2 is suspended by a suspension ring 17, is wound in or out, thereby transporting the support pan 28 carrying the desired compact disc to above the player 1.
Next a solenoid 36 is activated, moving an actuator plate 34 towards the elevator 2 (toward the lower right in the figure) against the compressive force of a tension spring 35. If a rotating shaft 48 of a motor 47 is rotated under these conditions, pulleys 45 and 46, over which a belt 49 has been passed, rotates, thereby transmitting driving power to drive wheels 43 and 44 by means of idlers 41 and 42, which provides a pressure contact with the pulleys 45 and 46. The support pan 28 is brought into pressure contact to the drive wheels 43 and 44 and is moved from the magazine rack 2 to the elevating frame 8 of the player 1. In the elevating frame 8, the support pan 28 is transported along guide grooves 11 and 12, after which the motor 56 is activated lowering the elevating frame 8 and placing the compact disc on turntable 6. At this time the pressure ring 9 is also lowered, holding the compact disc on top of turntable 6. Optical pickup 7 is then moved to the player 1, upon which the compact disc rests, where it reads information from the disc and sends the information read to the reproducing circuit (not shown).
After completion of the performance, the motor 56 is activated raising the elevating frame 8 and the pressure ring 9, and the carrier 4 is activated to return the support pan 28 to its previous location in the magazine 3.
Again, FIG. 89 is a vertical cross-sectional diagram showing a conventional disc-chucking apparatus as disclosed, for example, in Japanese Utility Model Kokai Publication No. 193560/1986 (Showa 61-193560). FIG. 90 is a vertical cross-sectional diagram showing this conventional disc-chucking apparatus with a disc resting thereon, in which a reference numeral 1021 designates the base of the apparatus; 1022 a spindle fixed to the base 1021; 1023 a disc that is the medium for recording a video, audio or other signal and has at its center a clamping plate 1042 formed from a soft magnetic material; 1031 a cartridge accommodating a disc 1023; 1024 a support piece, which positions the disc 1023 in the vertical direction; 1025 a centering piece that acts to position the disc 1023 in the radial direction; 1026 a guide piece having an inclined portion for guiding the centering piece 1025 when the disc 1023 is to be loaded into the apparatus; 1027 a chucking magnet, having either the single magnetic domain structure shown in FIG. 91 or the striped magnetic domain structure shown in FIG. 92, for attracting the disc 1023 into intimate contact with the support piece 1024; 1028 a turntable comprising the support piece 1024, the centering piece 1025, the guide piece 1026 and the chucking magnet 1027; 1029 a bearing supporting turntable 1028 in its rotation around spindle 1022; and 1030 a motor to drive the turntable 1028 in its rotation.
The motor 1030 is held stationary on the base 1021 and is provided with a core 1062 wound with a coil that is not shown, a rotor 1063 that rotates together with turntable 1028, and a magnet 1064 fixed to the rotor 1063.
FIG. 93 is a conceptual diagram showing one example of a disc loading and unloading apparatus for a recording and reproducing apparatus using a disc-chucking apparatus, in which a reference numeral 1032 designates a holder holding the cartridge 1031; 1033 a pivot constituting the center of rotation of the holder 1032; 1034 a spring to make the holder 1032 rotate in the clockwise direction; 1035 a engagement portion provided on the holder 1032; 1036 a hook; 1037 a pivot constituting the center of rotation of the hook 1036; 1038 a spring to apply pressure to rotate the hook 1036 in the counterclockwise direction; 1039 a positioning pin to act as a positioning member for the cartridge 1031; 1040 a holding member to press and hold the cartridge 1031 provided on the holder 1032 against the recording and reproducing apparatus; 1041 a spring for the same; and 1043 a disc loading apparatus comprising the components listed above.
Following is a description of the operation. The disc 1023 is loaded into the recording and reproducing apparatus by disc loading apparatus 1043. Referring to FIG. 93, if the cartridge 1031 is inserted in the holder 1032 and the holder 1032 is pressed downwards, the hook 1036 is engaged with engagement portion 1035 of the holder 1032, keeping it stationary with respect to the recording and reproducing apparatus. Meanwhile the cartridge 1031 is pressed and held against the positioning piece 1039 of the base 1021 by the pressure piece 1040. At this time, the disc 1023 is guided by the guide piece 1026 of the turntable 1028, and its position is determined by the centering piece 1025 and the support piece 1024 so that it is separated from the support piece inside cartridge 1031, and the clamping plate 1042 is attracted by the chucking magnet 1027 so that it is fixed to the turntable 1028. The turntable 1028 is then driven in a rotary manner by the motor 1030 and the signal is recorded or reproduced by means of a magnetic head or optical head.
FIG. 94 is a plan view showing the structure of a conventional position-detecting apparatus as disclosed, for example, in Japanese Patent Kokai Publication No. 32246/1986 (Showa 61-32246), in which a reference numeral 1354 designates a motor; 1371 a worm gear held with respect to the rotating shaft of the motor 1354; and 1351 a slider capable of moving in the directions indicated by arrows 1351A and 1351B. A reference numeral 1353 designates a contact gear having contacts 1391 (FIG 96) on the reverse surface; and 1370 a position-detecting circuit board having an arcuate pattern 1392 (FIG. 95) of the obverse surface. A reference numeral 1372 designates a transmission gear train that engages with worm gear 1371 and transmits driving power form the motor 1354; 1380 a drive gear that engages transmission gear train 1372 and drives contact gear 1353; and 1356 a drive gear that engages with the contact gear 1353 to drive the slider 1351. A reference numeral 1375 designates the spindle of the drive gear 1380; 1352 the spindle of the contact gear; and 1387 the spindle of the drive gear 1356.
FIG. 95 is a plan view showing an arcuate pattern 1392 on a position-detecting circuit board 1370 of the conventional position-detecting apparatus, in which a reference numeral 1392 designates the arcuate pattern for position detection; 1393 a common electrode; and 1394, 1395 and 1396 detection electrodes.
FIG. 96 is a vertical cross-sectional diagram showing the contact gear of the conventional position-detecting apparatus, and FIG. 97 is a view taken along a line S97--S97 in FIG. 96, in which a reference numeral 1391 designates position-detecting contacts.
Following is a description of the operation. The rotational driving power of the motor 1354 is transmitted from the worm gear 1371 through transmission gear train 1372 to the drive gear 1380 to drive contact gear 1353. The drive gear 1356 is also driven rotationally by the contact gear 1353 to drive the slider 1351. The stopping point for the slider 1351 is detected when the contacts 1391 on the reverse surface of the contact gear 1353 come into friction contact with the arcuate pattern 1392 on the top of the position-detecting circuit board 1370 so that a current path is established between common electrode 1393 and one or two of detection electrodes 1394, 1395 and 1396, thereby providing the prescribed signal output.
However, a problem with the conventional automatic disc-changing apparatus shown in FIG. 88 is that the drive mechanism that imparts vertical motion to the elevating frame, the drive mechanism that imparts vertical motion to the elevator, and the drive mechanism, which transports the support pan on which the compact disc rests are individually provided with motors, and a solenoid is specially provided to provide pressure contact of the carrier pulley against the support pan, so that the structure is complicated and the cost of the apparatus is high.
An additional problem is that when the support pan is transported from the magazine rack to the player, vertical motion is imparted to the elevator, in which the support pans are stacked in the height direction, but since the moving elevator is of great volume (or its height dimension is large), the apparatus is too large to be installed in automobiles.
A further problem is that replacing the compact discs in the magazine rack requires a two-step procedure in which the magazine rack is first removed from the elevator and the support pans in the magazine rack are then withdrawn, making it inconvenient to use.
In the conventional disc-chucking apparatus shown in FIG. 89 through FIG. 93, the disc 1023 is attracted by the chucking magnet 1027, which is fixed to the turntable 1028. For this reason, in removing the disc 1023 from the turntable 1028, the hook 1036 is rotated clockwise as seen in FIG. 93 either manually or by a motor or other actuator to release engagement portion 1035.
When this occurs, the holder 1032 leaps upward due to the action of spring 1034. At this point the holder 1032 must pull the disc 1023 upward against the attractive force of the chucking magnet 1027, requiring that the spring force of the spring 1034 be greater than the sum of the attractive force of the chucking magnet 1027 and the weights of the cartridge 1031 and the holder 1032. This results in a problem in that any increase in the attractive force of the chucking magnet 1027 requires an increase in the force required to load the holder 1032 into the apparatus, adversely affecting the operational feel. Further if the attractive force of the chucking magnet 1027 is too small, a problem arises in that the force holding the disc 1023 to the turntable 1028 is reduced, so that when the apparatus is acted upon by vibration or other external disturbance, disc 1023 is easily separated from turntable 1028, rendering the accurate reading of the signals difficult.
Another problem with the conventional disc-chucking apparatus is that turntable 1028 is supported on a spindle 1022, which is fixed to base 1021, so that when the apparatus is acted upon by vibration or other external disturbance, vibration is transmitted to the turntable 1028 and applied to the disc 1023, rendering the accurate reading of the signals difficult.
Another problem with the conventional disc-chucking apparatus is that it requires two magnets: a magnet 1064, which is used in the motor 1030 for the rotating of the turntable 1028, and a chucking magnet 1027 for attracting and holding the disc 1023, with the result that the number of components is increased and costs rise.
Another problem with the conventional disc-chucking apparatus is that it requires two holding members: rotor 1063 for holding magnet 1064 of the motor 1030, and the turntable 1028 for holding the chucking magnet 1027, with the result that the number of components is increased and costs rise.
Yet another problem with the conventional disc-chucking apparatus is that it requires a great deal of force to remove the the clamping plate 1042 that is attracted to the chucking magnet 1027 from the apparatus.
Again, in the conventional position-detecting apparatus shown in FIG. 94 through FIG. 97, is that the stopping point is detected when contacts 1391 on the reverse surface of the contact gear 1353 come into friction contact with the arcuate pattern 1392 on the top of position-detecting circuit board 1370 so that a current path is established between common electrode 1393 and one or two of detection electrodes 1394, 1395 and 1396. This raises a problem of reliability, in that there is a danger of faults occurring due to wear or corrosion of contacts 1391 or arcuate pattern 1392.
Further, letting P be the number of position detection points and n be the requisite number of contacts (including common contacts), the requisite number of contacts n may be found by rounding up m, wherein EQU m=log.sub.2 (p+2)
In general the number of the detection points P is two, at the beginning and at the end, so that the minimum number of contacts n required is two. Also contacts 1391 must be arranged along the radius of the contact gear 1353. This raises a problem in terms of the compactness of the apparatus, in that the contact gear 1353 is enlarged in the radial direction.